Abstract

Abstract
In this work we present a review of all-optical XOR gates based on Mach-Zehnder Interferometer with Semiconductor Optical Amplifiers (MZI-SOA), using NRZ modulated signals driven at 10 Gbit/s. The performance of two alternative schemes for logical XOR gates implementation is demonstrated through numerical simulations and experimentally. The extinction ratio shows high operation performance with low degradation. ©2009 IEEE.

Abstract
In this paper, we investigate experimentally the impact of optical amplifiers, namely Erbium Doped Fiber Amplifiers (EDFA) on Optical Burst Switching (OBS) networks, operating at 2.5 Gb/s (typical bit rate for current passive optical networks - PON). Bursts with 2(12) - 1 and 2(16) - 1 pseudo random binary sequence (PRBS) were studied, with different idle times (from 2 mu s to 80 mu s). The use of traffic with variable idle time was assessed in order to evaluate the effect on the burst initial amplitude. We also analyzed the performance of the packet based system by measuring the Q factor at the receiver and concluded that the performance is not affected by the type of traffic (variable or fixed idle times).

Abstract
Variable-length codes, using source statistical features, improve the encoding. However, using these codes can results in error propagation in bit string transmitted to noisy transmission environments. This paper has used reversible symmetrical codes in the bit string obtained from JPEG compressor in order to overcome this problem. several examples of reversible code design algorithm have been reviewed and a symmetrical code based on Huffman code has been analyzed and deigned for JPEG compressor Jpeg compressor has been simulated by Huffman standard code and by reversible symmetrical code and the amount of their compression has been compared for several pictures Also, optimization of detection trend in noisy condition has been displayed. © 2009 IEEE.

Abstract
Consider a wireless sensor network (WSN) where a broadcast from a sensor node does not reach all sensor nodes in the network; such networks are often called multihop networks. Sensor nodes take individual sensor readings, however, in many cases, it is relevant to compute aggregated quantities of these readings. In fact, the minimum and maximum of all sensor readings at an instant are often interesting because they indicate abnormal behavior, for example if the maximum temperature is very high then it may be that a fire has broken out. In this context, we propose an algorithm for computing the min or max of sensor readings in a multihop network. This algorithm has the particularly interesting property of having a time complexity that does not depend on the number of sensor nodes; only the network diameter and the range of the value domain of sensor readings matter. © 2009 pringer Science+Business Media B.V.

Abstract
This paper addresses sensor network applications which need to obtain an accurate image of physical phenomena and do so with a high sampling rate in both time and space. We present a fast and scalable approach for obtaining an approximate representation of all sensor readings at high sampling rate for quickly reacting to critical events in a physical environment This approach is an improvement on previous work in that after the new approach has undergone a startup phase then the new approach can use a very small sampling period.